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Bayard-Alpert
Gauges For UHV Systems
- Sealed and nude types
- Useful to measure vacuum in the range of 10-4 to10-9 torr
- Wide applications in mass spectrometers, surface analytical
instruments, thin film deposition units, accelerators and
other equipments operational in UHV systems.
Introduction
Bayard Alpert gauges (both sealed and nude types) are used
for measurement of low pressure in the range of 10-4 to 10-9
torr. This is achieved by measuring the ionisation current,
which decreases with the decrease in the pressure and is also
dependent on the type of the gas species present in the vacuum
system. These gauges come under the category of hot ionisation
vacuum gauges. It consists of a filament, an ion collector
and a grid. In sealed type gauges they are supported on a
glass wafer base having a number of glass to metal (GM) seals.
The metal pins apart from supporting the above components
are also used to provide electrical connections. The whole
assembly is housed in a glass envelope with wafer base fused
at one end. In nude type gauges, a tubular Kovar metal to
glass seal is welded to a standard SS flange. The tungsten
filament, molybdenum grid and the tungsten ion collector are
spot welded to the Kovar pins of the GM seal as in sealed
type gauges. This assembly is protected by a removable transparent
(acrylic) cover.
Technical Specification
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Filament
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:
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Tungsten
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Filament voltage
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:
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4.2 V
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Filament current
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:
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3.2 A
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Filament potential
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:
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+ 100 V DC
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Collector
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:
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Tungsten
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Collector potential
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:
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0 V DC
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Grid and Supports
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:
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Molybdenum
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Grid potential
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:
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+ 200 V DC
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Degass power for grid
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:
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30 to 40 Watts
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Pressure range
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:
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10 -4 to10 -9 torr
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Sensitivity
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:
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~ 12/ torr for Nitrogen
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Leakage current
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:
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~ 10 -12 A
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Envelope and tubulation material (For Sealed Gauge)
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:
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Kodial sealing glass
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Baking temperature: nude gauge/ sealed gauge
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:
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400 0 C/ 350 0 C
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Flange size for nude gauge
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:
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CF 35 (70 mm OD Conflat)
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Flange material
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SS 304
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Protection (For Nude gauge)
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:
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Perspex cover
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Application
These gauges are required for the measurement of vacuum in
the range 10-4 to10-9 torr. Such gauges are needed for mass
spectrometers, surface analytical instruments, thin film deposition
units, accelerators and all other equipments/ processes needing
ultra high vacuum. Apart from DAE, research institutions/
universities and some of industrial units using UHV systems
may find these vacuum gauges very useful.
For
further information please contact :
Head,
Technology Transfer & Collaboration Division,
Bhabha Atomic Research Centre,
Trombay, Mumbai - 400 085
Tel : 091-022-25505337/25593897
Fax : 091-022-25505151
E-mail : headttcd@barc.gov.in
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